Session studies potential threat

Group raises early guard against zebra mussels

In the beginning, it was locusts, then it was fire ants, then killer bees, then West Nile virus-infected mosquitoes. Now there's a new potential peril to the environment that scientists and researchers from the Upper Colorado River to the Gulf of Mexico are fighting: dreissena polymorpha, better known as zebra mussels.

A major workshop was held at the Lake Mead Lodge, Oct. 19, where federal and state water officials up and down the Colorado River met to discuss the threat and the real possibility that without education, inspections and cleanings, no body of water is totally immune from infestation.

"We feel if they arrive, Lake Mead can support them," said Kent Turner, chief of resource management for the Lake Mead National Recreation Area and coordinator for the workshop.

He said the water authority's Alfred Merritt water plant, the Hoover Dam power generators, the pipeline and diffuser from the Las Vegas Wash, boats and docks are all potential targets for zebra mussels, since they cling to hard surfaces and grow into giant clusters.

The tiny mollusks that can measure up to an inch or longer with a zebra-like shell have wreaked havoc on the East Coast and the Midwest since being introduced into the United States in 1988. Estimates put their economic toll in the Great Lakes region at hundreds of millions of dollars alone.

They pose a grave threat to the West if found immigrating from any of the 23 states or the two Canadian provinces where they're found. But an effort is afoot to stop the species from spreading westward from the 100th Meridian, especially into the Lake Mead National Recreation Area.

The 100th Meridian splits the Plains States of the Dakotas, Nebraska and Kansas, the Oklahoma Panhandle and West Texas.

"They have a high colonization rate in waters 18 to 25 degrees Celsius (or 64 to 77 degrees Fahrenheit) and moderate colonization at 25 to 28 degrees Celsius (or 77 to 82 degrees Fahrenheit)," Turner said. "These are all within the water temperatures found at Lake Mead. An analysis of the water parameters at Lake Mead show they're well within the range for (zebra mussels) to live here."

Turner added the mussels are filter feeders, meaning they filter out algae and all single-celled animals. Since these are at the bottom of the food chain and necessary for fish food, fishing can be seriously disrupted.

The Lake Mead official said that for the mussel to survive, it must be wet, since it can not live out of the water for long.

"One thing we've got going for us is, if someone is trailering a boat from an infected state," Turner said. "We feel if it's been out of water for a month, the probability of the zebra mussel larvae surviving is significantly low."

He said educating boaters and water enthusiasts is a must since the National Park Service doesn't have the personnel to perform hundreds of boat inspections, but does what it can by asking motorists trailering boats where they're coming from and whether they're aware of the zebra mussel problem.

Marina operators, boat brokers and others involved in the marine industry are urged to conduct voluntary inspections as a means to help control the potential problem.

There is no mandatory inspection process in place.

Still, the zebra mussel, despite all the attention and concern and the various means of controlling the population, worries officials that some day an infested or encrusted boat will slip into Lake Mead and start the spread of the almost-uncontrollable nuisance.

"The zebra mussel is one of 10 to 15 species that's high on our radar screen and an even higher probability to spread since you never know where it's going spread," Turner said. "Once there's an infestation, you're into mitigation and management of something you can't change or eradicate. Once they're here, if they get here, the concern of ours is what best can we do to prevent them from spreading elsewhere."


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